Convert String to Integer

Code

#include <stdio.h>
#include <stdint.h>

int custom_atoi(const char *str) {
   if(str[0]=='+' || str[0]=='-' || (str[0]>='0' && str[0]<='9'))
   {
    if(str[0]>='0' && str[0]<='9')
    {
        int i=0,t=0;
        while(str[i]>='0' && str[i]<='9' && str[i]!='\0')
           {t=t*10 + str[i]-'0';
           i++;}
           return t;
    }
    else if(str[1]>='0' && str[1]<='9')
    {
        int i=1,t=0;
        while(str[i]>='0' && str[i]<='9' && str[i]!='\0')
           {t=t*10 + str[i]-'0';
           i++;}
           if(str[0]=='-') t*=-1;
           return t;
    }
    else
      return 0;
   }
    return 0;
}

int main() {
    char str[101];
    fgets(str, sizeof(str), stdin);

    // Remove newline
    uint8_t i = 0;
    while (str[i]) {
        if (str[i] == '\n') {
            str[i] = '\0';
            break;
        }
        i++;
    }

    printf("%d", custom_atoi(str));
    return 0;
}

Solving Approach